Work transfer device

ABSTRACT

Relating to improvement in a hand of an apparatus for taking out a workpiece such as liquid crystal glass from a cassette and carrying it to a predetermined position, and aiming at reducing a weight of an arm portion for holding the liquid crystal glass and a quantity of deflection. A workpiece holding portion of the hand for holding a workpiece such as liquid crystal glass is formed by a horizontal holding arm ( 5 ) extending in the horizontal direction and consisting of a carbon fiber material, the horizontal holding arm ( 5 ) has a horizontal arm portion ( 7 ) opposed to the workpiece and at least one bent portion ( 6 ) being bent in a direction crossing the horizontal arm portion ( 7 ), and a surface of a corner portion ( 5   d ) on the border between the bent portion ( 6 ) and the horizontal arm portion ( 7 ) is rounded.

TECHNICAL FIELD

The present invention relates to a workpiece carrying apparatus. Moreparticularly, the present invention relates to improvement in a shape ora material of an apparatus for taking out a workpiece such as liquidcrystal glass from a cassette and carrying it to a predeterminedposition.

BACKGROUND ART

A workpiece carrying apparatus 101 for carrying a workpiece such asliquid crystal glass has, for example, a base 102, a first arm 103, asecond arm 104 and a hand 105 as shown in FIG. 13. In this case, as aportion of the hand 105 for holding a workpiece (which will be simplyreferred to as a workpiece holding portion 105 hereinafter), a thin andelongated one which can carry a relatively large workpiece 106, enter agap between the workpieces 106 piled up in the multilayer form at anarrow accommodation pitch and take out such a workpiece is preferable.Further, it is important that the workpiece holding portion 105 has thesufficient rigidity for reducing the deflection when holding theworkpiece 106 and it is formed to be lightweight.

As such a workpiece holding portion 105, there is a flat bar obtainedby, e.g., scraping off an aluminium material or carbon and molding it.As things stand now, as a material of the workpiece holding portion 105,aluminium or carbon mentioned above, stainless steel or ceramics is usedto intend reduction in weight and provide the sufficient strength.

In recent years, however, with increase in size of the workpiece 106,the size of the workpiece holding portion 105 of the workpiece carryingapparatus 101 is also increased, and increase in weight of the workpieceholding portion 105 or the deflection involved by this increase becomesa problem. When the workpiece holding portion 105 is deflected in thismanner, the workpiece 106 can not be safely and securely inserted orremoved unless the accommodation pitch of the workpiece 106 in thecassette is increased. Furthermore, since the rectilinear movementproperty at the time of inserting or taking out the workpiece holdingportion 105 is deteriorated because of the deflection, a moving velocitymust be reduced, thereby prolonging the tact time required for carryingthe workpiece 106. Moreover, the inertia also becomes large when theweight of the workpiece holding portion 105 is increased, and increasingan output for driving the workpiece holding portion 105 may result inenlargement of the dimension of the entire apparatus.

In addition, the workpiece holding portion 105 of the workpiece carryingapparatus 101 must have the structure for sucking the workpiece 106,i.e., a pad, a rubber material, a pipe, a sensor cable and others. It isrequired to accommodate these members while obtaining the thin shape asa whole. As such a thin workpiece holding portion 105, there is onehaving, e.g., a rectangular cross section. However, since such aworkpiece holding portion 105 is formed by scraping off a solid-corematerial, the workpiece holding portion 105 itself has the solid-corestructure. Thus, when the workpiece holding portion 105 is formed to belong in the longitudinal direction, the workpiece holding portion 105may be deflected downwards by action of the uniformly distributed loadby its own weight. In this case, a quantity of deflection becomesmaximum at the end of the workpiece holding portion 105. Additionally,if its influence is considerable, the accuracy for inserting theworkpiece holding portion 105 between the workpieces 106 is lowered.

It is, therefore, an object of the present invention is to provide aworkpiece carrying apparatus which can be formed long while suppressingincrease in weight of a workpiece holding portion for holding aworkpiece, and which has the rigidity bearing off elongation. That is,it is an object of the present invention to form the workpiece holdingportion as a long product which is lightweight and hardly deflected.

DISCLOSURE OF INVENTION

To achieve this aim, according to the present invention, there isprovided a workpiece carrying apparatus comprising a hand for holding aworkpiece and a moving mechanism for moving the hand in the horizontaldirection, wherein a workpiece holding portion of the hand is formed bya horizontal holding arm which is extended in the horizontal directionand consists of a carbon fiber material, the horizontal holding arm hasa horizontal arm portion opposed to a workpiece and at least one bentportion bent in a direction crossing the horizontal arm portion, and thesurface of a corner portion on the border between the bent portion andthe horizontal arm portion is rounded.

In this case, the horizontal holding arm is originally molded in shapesuch that a plate-like member is bent. As a result, a space is formed ina concave portion having a bent shape, and members required for suckinga workpiece are accommodated in this space. Therefore, the horizontalholding arm can be formed thin and compact as a whole whileaccommodating the respective members. Furthermore, when the plate-likemember has the bent shape, the high flexural rigidity can be obtained.Moreover, in the present invention, since this horizontal holding arm isconstituted by a carbon fiber material, the weight can be reduced andthe high rigidity can be obtained. According to the present invention,the workpiece holding portion of the hand can be elongated whilesuppressing increase in weight, and the rigidity bearing off elongationis provided. Thus, a quantity of deflection when holding a workpiece issmall, and a workpiece accommodated with a narrow pitch can be rapidlyand assuredly carried.

In addition, since the surface of the bent portion on the workpiece sideis rounded, interference hardly occurs even if the held workpiece iscurved. Even if the workpiece is brought into contact with the bentportion, the surface of the workpiece is prevented from being damaged,and the static electricity is rarely generated to the liquid crystalglass as a workpiece.

According to the present invention, the horizontal holding arm isprovided with the bent portions on both sides of the horizontal armportion in the workpiece carrying apparatus, as described previously. Inthis case, the geometrical moment of inertia can be increased, and theflexural rigidity which is high for a cross sectional area can beobtained. When the horizontal arm portion is caused to be orthogonal tothe bent portion in particular, the geometrical moment of inertia can befurther increased.

Furthermore, when a space is formed on the back side of the horizontalarm portion and used so that the members and others required for suctioncan be accommodated in this space, a thin and compact workpiece holdingportion can be formed.

According to the present invention, the horizontal holding arm isprovided with a flange portion which is bent on the opposite side to thehorizontal arm potion of the bent portion in the workpiece carryingapparatus as described above. In this case, the geometrical moment ofinertia can be further increased, and the high flexural rigidity can beobtained. Moreover, since the flange portion is formed at least on oneside of the horizontal holding arm, the geometrical moment of inertiacan be further increased and the high flexural rigidity can be obtained.

According to the present invention, the flange portion is bent outwardin the workpiece carrying apparatus described above. In this case, thehorizontal holding arm has a crank-like or Z-shaped cross section formedby the horizontal arm portion, the bent portion and the flange portion,and the high geometrical moment of inertia can be obtained.

According tot he present Invention, the horizontal holding arm has atransverse cross section which is hollow elliptical. When the closedshape is used in this manner, the cross-sectional shape is hardlydeformed, and a quantity of deflection at the end of the horizontalholding arm constituting the workpiece holding portion is small.Therefore, this is preferable as a large workpiece carrying apparatus inwhich the work holding portion is elongated.

According to the present invention, a suction portion for sucking aworkpiece is caused to protrude on the front surface side of thehorizontal arm portion and a holding mechanism for holding the suctionportion and a pipe for suction are accommodated on the back surface sideof the horizontal arm portion in the workpiece carrying apparatus asabove. According to this apparatus, a workpiece can be carried whilebeing sucked, and it is possible to form the thin work piece holdingportion having the compact shape in which the holding mechanism andothers are accommodated.

According to the present invention, the holding mechanism isaccommodated in a space consisting of a concave portion formed betweenthe horizontal arm portion and hte bent portion on the back surface sideof the horizontal arm portion in the workpiece carrying apparatus asdescribed above. When, e.g., taking out a workpiece, therefore, even ifthe workpiece is brought into contact with the back surface side of thehorizontal holding arm, the surface of the workpiece can be preventedfrom being damaged by the holding mechanism.

According to the present invention, a workpiece is a laminated platematerial, the horizontal arm portion includes a plurality of suctionportions, and the laminated plate material is sucked and held by aplurality of the suction portions in the workpiece carrying apparatus asdescribed above. Therefore, the plate material can be stably carried,and it is possible to cope with a plate material such as liquid crystalglass.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a transverse cross-sectional view of a horizontal holding armshaped like a top hat showing an embodiment according to the presentinvention;

FIG. 2 is a plane view of a workpiece carrying apparatus;

FIG. 3 is a front view of the workpiece carrying apparatus;

FIG. 4 is a side view of the workpiece carrying apparatus;

FIG. 5 is a plane view showing the workpiece carrying apparatus on adirect acting mechanism;

FIG. 6 is a view schematically showing the cross-sectional shape of thehorizontal holding arm shaped like a high hat;

FIG. 7 is a table showing an example in which the dynamiccharacteristics of the horizontal holding arm according to thisembodiment adopting CFRP as a material of the horizontal holding armwith those of the conventional horizontal holding arm consisting ofaluminium;

FIGS. 8A, 8B and 8C are views and a table in which the geometricalmoment of inertia of the horizontal holding arm having a cross sectionlike a channel is compared with that of the horizontal holding armhaving a cross section like a top hat;

FIG. 9 is a transverse cross-sectional view of a horizontal holding armshowing another embodiment according to the present invention;

FIG. 10 is a view showing the horizontal holding arm attached to a handbase portion;

FIG. 11 is a view showing a deflected workpiece and the horizontalholding arm holding this workpiece;

FIG. 12 is a schematic view showing the horizontal holding arm havinganother shape; and

FIG. 13 is a perspective view showing a conventional workpiece carryingapparatus.

BEST MODE FOR CARRYING OUT THE INVENTION

The structure of the present invention will now be described in detailbased on an embodiment shown in the accompanying drawings. FIGS. 1 to 8show an embodiment of a workpiece carrying apparatus according to thepresent invention. As shown in FIGS. 2 and 3, this workpiece carryingapparatus 1 includes a hand 14 for holding a workpiece 2, and a movingmechanism 4 for moving the hand 14 in the horizontal direction. Themoving mechanism 4 includes a base 13, a first arm 11 capable ofrotating on the base 13, and a second arm 12 rotatably attached to theend of the first arm 11. Further, the rotatable hand 14 is attached tothe end of the second arm 12. The height of the part from the first arm11 to the hand 14 can be adjusted by moving up and down the first arm 11as shown in FIG. 4. Furthermore, the base 13 is mounted on a directacting mechanism 21 shown in FIG. 5 and linearly moves. Moreover, whenthe hand 14 is rotated at the end of the second arm 12 withoutrestraint, a desired workpiece 2 can be taken out or carried.

The hand 14 is provided with a workpiece holding portion 3 which issupported by a hand base portion and holds a workpiece 2. In thisembodiment, the workpiece holding portion 3 is constituted by a pair ofhorizontal holding arms 5 which extend in parallel to each other in thehorizontal direction and have the same height as shown in FIG. 2 or 4.

Each horizontal holding arm 5 has a horizontal arm portion 7 consistingof a flat plane opposed to the workpiece 2 and at least one bent portion6 which is bent in a direction crossing the horizontal arm portion 7,and a corner portion 5 d on the border between the bent portion 6 andthe horizontal arm portion 7, namely, the surface of the bent portion 6on the workpiece side 2 is rounded. Here, although it is preferable thatthe bent portion 6 is bent so as to be orthogonal to the horizontal armportion 7, it may be bent so as to be oblique or form a curved surfacesuch as shown in FIG. 9 in some cases.

In addition, the horizontal holding arm 5 constituted by the horizontalarm portion 7 and at least one bent portion 6 can suffice. However, forexample, the horizontal holding arm 5 including a flange portion 5 bshaped like a channel as shown in FIG. 8A is preferable, and thatincluding a flange portion shaped like a top hat such as shown in FIG. 6or FIG. 8B is more preferable. The horizontal holding arm 5 shown inFIG. 6 or 8B has a shape for simultaneously forming the horizontal armportion 7 and the bent portion 6 by causing the central portion in thewidthwise direction to protrude upward. That is, the horizontal holdingarm 5 has a groove shape having the horizontal arm portion 7 and thebent portions 6 extending from both sides of the horizontal arm portion7 downward in the vertical direction.

Additionally, it is preferable that the end of the bent portion 6 on theside away from the horizontal arm portion 7 is bent outward or inward tobe formed as a flange portion 5 b. In the horizontal holding arm 5 shownin FIG. 6, the lower end sides of the bent portions 6 on the both sidesare bent outward, thereby forming the flange portions 5 b. Here, in thehorizontal holding arm 5 shown in FIG. 6, each flange portion 5 b is ahorizontal plane bent in a direction orthogonal to the bent portion 6.

It is to be noted that the cross-sectional shape of the horizontalholding arm 5 is not necessarily restricted to one symmetrically havingthe bent portions 6 and the flange portions 5 b on the both sides of thehorizontal arm portion 7. For example, providing the bent portion 6 atleast on one side can suffice. Further, the bent portion 6 does not haveto be a plane parallel to the horizontal arm portion 7, and it may beone extending in, e.g., the oblique direction. However, the shape shownin FIG. 6 is preferable for increasing the geometrical moment of inertiaof the horizontal holding arm 5 and obtaining the high flexuralrigidity.

Furthermore, the horizontal holding arm 5 in this embodiment has a shapethat the plane of the corner portion 5 d on the border between the bentportion 6 and the horizontal arm portion 7 is rounded. In this manner,interference hardly occurs on the outer peripheral surface of the curvefrom the horizontal arm portion 7 to the bent portion 6 even if theworkpiece 2 held by the two horizontal holding arms 5 is curved. Even ifthe workpiece is brought into contact with that surface, the surface ofthe workpiece 2 can be prevented from being damaged, and the staticelectricity is rarely generated on the liquid crystal glass as theworkpiece.

Moreover, the horizontal holding arm 5 having the above-described shapehas a space 5 c consisting of a concave portion between the bentportions 6 on the back surface side of the horizontal arm portion 7. Inthis embodiment, members such as a holding mechanism 9 for holding asuction portion 8 and a sensor cable 27 are accommodated in this space 5c. The suction portion 8 is, for example, a suction cup which sticksfast to the surface of the workpiece 2 and holds it.

As shown in FIG. 1, in this embodiment, a through hole 15 is provided tothe horizontal arm portion 7 so that the suction portion 8 can slightlyprotrude therefrom to the front side of the horizontal arm portion 7.Further, a holding mechanism 9 for holding the suction portion 8 and asuction pipe 10 which is connected with a non-illustrated vacuum sourceand sucks air from an air chamber 23 are accommodated on the backsurface side of the horizontal arm portion 7. The through hole 15 ismatched with a peripheral surface shape of the suction portion 8provided in the hole, and formed by a cone-shaped inclined plane thatthe diameter of the lower part is smaller than that of the upper part asshown in FIG. 1.

Furthermore, in this embodiment, since a space 5 c surrounded by thebent portion 6 on the back surface side of the horizontal arm portion 7is opened, the operation for accommodating the suction portion 8, theholding mechanism 9, the sensor cable 27 and others can be easilyperformed.

The holding mechanism 9 is provided in order to hold the above-describedsuction portion 8 from the lower side, and it is constituted by aventilation member 17, a support member 18, a sealing member 19, anengagement member 20, a suction pipe 10 and spring means 22 in thisembodiment.

The ventilation member 17 is a cylindrical member provided with a flangeportion 17 a as shown in the drawing and fitted into the hole at thecenter of the suction portion 8 from the lower side. Moreover, when thesuction portion 8 and the support member 18 are sandwiched by theengagement member 20 fitted in a tubular groove and the flange portion17 a, the ventilation member 17 is air-tightly brought into contact withthe support member 18 to integrate these members. The ventilation member17 has a ventilation hole 17 b at the center thereof, and air in theconcave portion 8 a is taken in and out from this ventilation hole 17 bto cause the negative pressure to act. A step portion for holding theend of the spring means 22 is provided in this ventilation hole 17 b.The spring means 22 is provided between the ventilation member 17 andthe sealing member 19 and constantly gives impetus to the suctionportion 8 upwards through the ventilation member 17. Although a coilspring is used as this spring means 22 for example, any other springmeans, e.g., a belleville-spring or a flat spring may be used to giveimpetus.

The support member 18 has a hole at the center and elastically supportsthe suction portion 8 and the ventilation member 17 fitted in thiscentral hole. When this support member 18 is formed of silicon rubber,it has the elasticity such that the part on the inner peripheral side inthe vicinity of the central hole rotates so as to move in the verticaldirection or twist in the horizontal direction and inclination ischanged in the front-and-back direction or the right-and-left direction.Also, the support member 18 can air-tightly come into contact with theflange portion 17 a. Further, the support member 18 can also air-tightlycome into contact with the sealing member 19.

The sealing member 19 is formed into a groove shape as shown in thedrawing, and attached so as to hold the support member 18 from the lowerside. Furthermore, the sealing member 19 air-tightly comes into contactwith the support member 18 to form an air chamber 23. The sealing member19 is screwed from the lower side by screws 24 and 24 which reach thehorizontal arm portion 7 of the horizontal holding arm 5, and fixed tothe horizontal holding arm 5 together with the support member 18 andothers. Moreover, the sealing member 19 has a groove portion forinstalling the suction pipe 10 at the inner central portion thereof.

The holding mechanism 9 having such a structure can release air with thesuction portion 8 being in contact with the lower surface of theworkpiece 2, and suck the workpiece 2 by forming a negative pressure inthe air chamber 23. At this moment, since the suction portion 8 and thesupport member 18 have the elasticity, the suction portion 8 can changethe inclination of the suction plane in the front-and-back direction orthe right-and-left direction. In addition, the suction portion 8receives the upward force by the spring means 22. Therefore, grantingthat the workpiece 2 is curved, the suction portion 8 can entirely comeinto contact with the lower surface of the workpiece 2 to form anegative pressure in the air chamber 23. Additionally, when the supportmember 18 receives the weight of the workpiece 2 and a negative pressureis formed in the air chamber 23, the support member 18 is deflecteddownward, and the suction portion 8 and the ventilation member 17 dropdownward. However, since they continuously receive the upward force bythe spring means 22, they are not lowered beyond a predeterminedposition. Thus, it is possible to prevent the lower surface of theworkpiece 2 from coming into contact with the horizontal arm portion 7of the horizontal holding arm 5 and from being damaged. Further, thesuction portion 8 which is elastically supported by the support member18 and the spring means 22 which consist of elastic members absorbs theimpact at the time of contact in order to suck the workpiece 2, and thesurface of the workpiece 2 is not thereby damaged.

Furthermore, in this embodiment, in the space 5 c of the horizontalholding arm 5 are provided an air pipe 25, a pipe holder 26 and othersas well as the above-described holding mechanism 9. The air pipe 25 issupported from the lower side by the plate-like pipe holder 26 fixed tothe lower surface of the sealing member 19. In case of providing such anair pipe 25, the suction pressure in the suction portion 8 can becontrolled in two systems by setting the air pipe 25 separately from thesuction pipe 10. Moreover, sensor cables 27 for transmitting a detectionsignal of the workpiece or the like are provided at a positionsymmetrical with respect to the air pipe 25 and similarly supported bythe pipe holder 26.

Incidentally, a plurality of the through holes 15 and suction portions 8are provided to the horizontal holding arm 5, and a laminated workpiece2 can be sucked and held by a plurality of the suction portions 8 asshown in FIG. 2. In this case, the number or installation positions ofthe suction portions 8 are not specifically restricted, and they can beappropriately changed depending on the dimension or shape of theworkpiece 2 as a target.

As described above, the horizontal holding arm 5 according to thisembodiment forms the horizontal arm portion 7 protruding toward theworkpiece 2 by forming the bent portion 6 in a direction away from theworkpiece 2, and includes the space 5 c on the back surface side of thehorizontal arm portion 7. This space 5 c is utilized to accommodate theholding mechanism 9 and others. In this case, it is preferable that thespace 5 c has a depth enabling the screw 24 to be accommodated from itshead portion and has a shape such that the entire horizontal holding arm5 can be thin as much as possible. By doing so, it is possible to entera narrow gap between the superimposed workpieces 2 at intervals. Inaddition, granting that the lower part of the horizontal holding arm 5is brought into contact with the upper surface of the workpiece 2, thesurface of the workpiece 2 is hardly damaged if the head portion of thescrew 24 does not protrude from the lower surface of the flange portion5 b.

Additionally, the horizontal holding arm 5 according to this embodimentincludes the horizontal arm portion 7, the bent portions 6 and theflange portions 5 b as mentioned above and has the high flexuralrigidity. That is, the bent portions 6 are provided in the verticaldirection on the both sides of the horizontal arm portion 7, and thehorizontal holding arm 5 according to this embodiment having thehorizontal flange portions 5 b has the geometrical moment of inertiawhich is large for the cross-sectional area and the high flexuralrigidity. In other words, a quantity of material used for the horizontalholding arm 5 is small and the entire weight can be reduced, whichresults in the synergistic effect that the uniformly distributed loadcaused by its own weight can be further reduced.

Incidentally, as shown in FIGS. 8A, 8B and 8C, it can be understood thegeometrical moment of inertia can be increased by forming the flangeportions 5 b even if the cross-sectional area remains the same. Further,since the rigidity becomes high when a ratio of the horizontal armportion 7 and the flange portion 5 b is 1:1, a shape which is preferablefor the strength can be obtained, but the present invention is notrestricted thereto.

Here, in the light of the rigidity of the horizontal holding arm 6, apreferable shape is illustrated in FIG. 8. As shown in FIG. 8B, assumingthat a width of the horizontal arm portion 7 is A and a width of theflange portion 5 b is B, when the geometrical moment of inertia iscalculated with the ratio of A:2B being changed, it can be understoodthat the geometrical moment of inertial becomes maximum and the rigiditybecomes high with A:2B being 1:1, as shown in FIG. 8C. Incidentally,although the value (1913) of the geometrical moment of inertia of a tophat type shape shown in FIG. 7 is different from the value depicted inFIG. 8C, this difference is caused due to a small difference indimension such as the R shape of the corner.

FIG. 9 shows an example of another embodiment indicating the structureof the present invention. It is to be noted that like reference numeralsdenote parts having the structure/principle which is basically the sameas the structure described in connection with the above embodiment,thereby omitting their explanation.

It is characteristic that the horizontal holding arm 5 shown in FIG. 9is formed by a hollow pipe whose cross section is elliptical.Specifically, the horizontal holding arm 5 includes a horizontal armportion 7 whose central part in the widthwise direction is flat as shownin the drawing, and the both sides of the horizontal arm portion 7constitute the bent portions 6 which are curved. In this case, thecorner portion ad on the border between the horizontal arm portion 7 andthe bent portion 6 is rounded by the circular shape of the bent portion9 itself. Furthermore, a part of the bent portion 6 which is downwardlybent toward the inner side constitutes the flange portion 5 b. In thisembodiment, as shown in FIG. 9, end portions of the flange portions 5 bon the both sides are connected, and the cross section forms anelliptical hollow pipe. It is to be noted that the ellipse in thisspecification is not restricted to the ellipse in the strict sense butincludes an elongated oval.

Incidentally, although not shown, in the horizontal holding arm 5 whosecross section is hollow, thin and rectangular, the upper surfacecorresponds to the horizontal arm portion 7, the both side surfacescorrespond to the bent portions 6, and the lower surface corresponds tothe flange portions 5 b. Moreover, the space 5 c is formed at a partsurrounded by the horizontal arm portion 7, the bent portions 6 and theflange portions 5 b.

In this embodiment, as similar to the embodiment shown in FIG. 1, athrough hole 15 is provided to the horizontal arm portion 7, and asuction portion 8 for sucking a workpiece 2 is caused to pass throughthis hole and protrude toward the front surface side. In addition, aholding mechanism 9 for holding the suction portion 8 and a suction pipe10 are accommodated in the inner space 5 c.

Incidentally, as shown in FIG. 9, a hole 5 e is formed on the lowersurface corresponding to the flange portions 5 b, and the operation forinstalling the suction portion 8 or the like is carried out from thishole 5 e. In this embodiment, the hole 5 e is provided on the backsurface side of the suction portion 8 or the like in accordance with theposition at which the suction portion 8 or the like is set.

Additionally, an insertion member which can be housed in the hollowportion of the horizontal holding arm a on the base side is inserted andattached to the hand base portion to which the horizontal holding arm 5is attached.

Further, the accuracy such as flatness of the horizontal holding arm 5is improved while providing a shim or the like for adjustment at thefastening part of the hand base portion to which the horizontal holdingarm 5 is attached.

If the horizontal holding arm 5 has such a closed shape as shown in FIG.9, since the cross-sectional shape is rarely deformed as compared withthe above-described embodiment (FIG. 1), a quantity of deflection at theend of the horizontal holding arm 5 is also smaller than that of theabove-described embodiment (FIG. 1). Therefore, the embodiment shown inFIG. 9 is preferable as the large workpiece carrying apparatus 1 inwhich the horizontal holding arm 5 is elongated.

Incidentally, although the above has described the cross-sectional shapeof the horizontal holding arm 5, the higher rigidity and furtherreduction in weight can be realized by appropriately selecting amaterial of the horizontal holding arm 5. For example, in the foregoingembodiment, a carbon fiber material (CFRP) is adopted as a material ofthe horizontal holding arm 5 so that reduction in weight can be achievedwithout deteriorating the strength as the workpiece holding portion 3.It is to be noted that, for example, FRP (fiber reinforced plastic)including GFRP (glass fiber reinforced plastic) can be also adopted insome cases.

Here, FIG. 7 shows an example of a result of comparison in dynamiccharacteristics between the horizontal holding arm 5 according to thisembodiment in which the carbon fiber reinforced plastic (CFRP) isadopted as a material and a conventional aluminium horizontal holdingarm. The length in the longitudinal direction, the width of the crosssection and the height are equal in the both arms. In this case, it canbe understood that the arm consisting of CFRP is superior in allcharacteristics as means for carrying the workpiece 2. For example, thearm consisting of CFRP has the Young's modulus (modulus of longitudinalelasticity) which is 2.5-fold or above of that of the arm consisting ofaluminium, and a quantity of deflection of the CFRP arm caused due toits own weight is greatly reduced (not more than ¼).

Further, in case of adopting CFRP as a material in this manner, it ispreferable to also consider the orientation of the fibers or coarsenessand minuteness. That is, in such a member as the horizontal holding arm5 according to this embodiment which is formed to be extended in thelongitudinal direction, increasing the density of the fibers arranged inthe longitudinal direction above that of the fibers arranged in thelateral direction orthogonal to the longitudinal direction is preferablefor enhancing the flexural rigidity. Furthermore, the fibers may bearranged in the oblique direction to improve the rigidity.

In the workpiece carrying apparatus 1 according to this embodimentdescribed above, the laminated workpiece 2 can be stably and assuredlycarried by the horizontal holding arm 5, and a thick glass workpiece 2or a workpiece 2 consisting of a material other than glass which has aweight can be also carried by providing the adequate strength to thehorizontal holding arm a.

Moreover, even if the horizontal holding arm a is further extended,increase in weight of the workpiece holding portion 3 formed by thishorizontal holding arm 5 can be suppressed and a quantity of deflectioninvolved by increase in weight can be reduced. Therefore, even if theaccommodation pitch of the workpiece 2 in the cassette is small, theworkpiece 2 can be stably and assuredly moved, and the rectilinearmovement property can be secured at the time of inserting or removingthe workpiece holding portion 3.

In addition, since the workpiece holding portion 3 according to thisembodiment is formed thin and the holding mechanism 9 or the like isaccommodated on the back surface side of the horizontal arm portion 7,the surface of the workpiece 2 can be prevented from being damaged.Additionally, the corner portion 5 d of the above-described horizontalholding arm 5 is rounded, and only the corner portion 5 d comes intocontact with the workpiece 2 even if the horizontal holding arm 5 isbrought into contact with the workpiece 2. Therefore, a problem ofdamages to the workpiece 2 does not occur.

Further, CFRP is adopted as a material of the horizontal holding arm 5.Thus, when the horizontal holding arm 5 is molded so as to have a crosssection shaped like a top hat, the mold which is divided in the verticaldirection can be used for molding, and the molding operation itself canbe facilitated. Furthermore, a quantity of material can be reduced inany embodiment described above, and it is possible to decrease the costin the long term while taking labors required for adjustment forreducing a quantity of deflection into consideration.

Incidentally, although the above has described a preferred embodimentaccording to the present invention, the present invention is notrestricted thereto. Various modifications can be carried out withoutdeparting from the scope of the invention. For example, the horizontalholding arm 5 described above can be applied to any workpiece carryingapparatus 1 which is of a single hand type shown in FIG. 2 or a doublehand type shown in FIG. 5.

Moreover, although the horizontal holding arm 5 according to thisembodiment has a shape including the flange portions 5 b, it is possibleto form the groove-like cross section such as shown in FIG. 8A in whichno flange portion 5 b is provided. However, since the horizontal holdingarm 5 according to this embodiment includes the flange portions 5 b at aposition lower than that of the suction portion 8, the rigidity can beincreased, and the possibility of contact with the workpiece 2 can bereduced. Also, attachment to the base portion of the hand 14 isfacilitated. That is, for example, by utilizing this flange portion 5 b,a screw can be inserted into a non-illustrated screw hole provided tothe flange portion 5 b shown in FIG. 10 so that the horizontal holdingarm 5 can be attached to the base portion of the hand 14. Alternatively,by utilizing the horizontal arm portion 7, the horizontal holding arm 5can be attached to the lower side of the base portion of the hand 14 asshown in FIG. 10. Further, when the vertical horizontal holding arms 5and 5 are attached to the double hand type workpiece carrying apparatus1 in such a manner that the horizontal holding arms 5 and 5 are invertedso as to be set back to back, this attachment can be facilitated byutilizing the flange portion. Therefore, in case of forming thehorizontal holding arm 5 into a groove-like shape having no flangeportion 5 b, the flange portion for attachment may be provided to onlythe attachment portion of the base portion of the hand 14. Furthermore,a reinforcement member may be superimposed on the flange portion 5 b andthen attached to the hand base portion.

Moreover, although the above has mainly described the embodiment of thehorizontal holding arm 5 having the bent portions 6 on the both sides,the horizontal holding arm portion 5 having at least one bent portion 6can suffice, and its shape does not have to be symmetrical. For example,as shown in FIG. 12, the horizontal holding arm 5 may have acrank-shaped cross section or a Z-shaped cross section in which onehorizontal arm portion 1 and one flange portion 5 b are connected toeach other through the bent portion 6. The flange portion 5 b isoutwardly bent on the opposite side to the horizontal arm portion 7. Incase of the shape shown in FIG. 12, its geometrical moment of inertia islarger than that of the groove-shaped horizontal holding arm 5 shown inFIG. 8A and the flexural rigidity is also higher than that of the same.Alternatively, although not shown, the flange portion 5 b may be benttoward the same side as the horizontal arm portion 7, namely, the innerside. In this case, the horizontal holding arm 5 has a channel-shapedcross section, the geometrical moment of inertia is increased and thehigh flexural rigidity a can be obtained. In addition, the holdingmechanism 9 and others are accommodated in the open space 5 c having twoplanes partitioned by the horizontal arm portion 7 and one bent portion6 as similar to each of the foregoing embodiments, and the suctionportion 8 is provided so as to slightly protrude from the horizontal armportion 7.

What is claimed is:
 1. A workpiece carrying apparatus comprising a handfor holding a workpiece and a moving mechanism for moving said hand in ahorizontal direction, wherein a workpiece holding portion of said handis formed by a horizontal holding arm extending in the horizontaldirection and consisting of a carbon fiber material, said horizontalholding arm has a horizontal arm portion being opposed to said workpieceand at least one bent portion being bent in a direction crossing saidhorizontal arm portion, a surface of a corner portion on a borderbetween said bent portion and said horizontal arm portion being rounded,a suction portion for sucking said workpiece protruding on a frontsurface side of said horizontal arm portion, and a holding mechanism forholding said suction portion and a suction pipe being accommodated onthe back surface side of said horizontal arm portion.
 2. The workpiececarrying apparatus according to claim 1, wherein said horizontal holdingarm has said bent portion on each side of said horizontal arm portion.3. The workpiece carrying apparatus according to claim 1, wherein saidhorizontal holding arm has a flange portion being further bent on a sideof said bent portion opposite to said horizontal arm portion.
 4. Theworkpiece carrying apparatus according to claim 3, wherein said flangeportion is outwardly bent.
 5. The workpiece carrying apparatus accordingto claim 2, wherein said holding mechanism is accommodated in a spaceconsisting of a concave portion formed between said bent portions on theback surface side of said horizontal arm portion.
 6. The workpiececarrying apparatus according to claim 1, wherein said workpiece is alaminated plate material, said horizontal arm portion is provided with aplurality of said suction portions, and said laminated plate material issucked and held by a plurality of said suction portions.
 7. A workpiececarrying apparatus comprising a hand for holding a workpiece and amoving mechanism for moving said hand in a horizontal direction, whereina workpiece holding portion of said hand is formed by a horizontalholding arm extending in the horizontal direction and consisting of acarbon fiber material, said horizontal holding arm has a horizontal armportion being opposed to said workpiece and at least one bent portionforming a curved surface and being connected to said horizontal armportion, said horizontal holding arm having a transverse cross sectionbeing hollow and elliptical, the horizontal arm portion includingsuction portions.